NEW YORK (Reuters) - Pension and endowment managers on Friday called on U.S. regulators to review the rules for shareholder voting after a firm collecting ballots for JPMorgan Chase & Co cut off polling information to the bank's opponents.

The Council of Institutional Investors, which represents managers of pensions, endowments, and foundations with more than $3 trillion of assets total, said in a letter to the Securities and Exchange Commission that votes at companies' annual meetings are set up in a way that gives too much of an advantage to corporate management.

A group of investors has proposed stripping JPMorgan head Jamie Dimon of his chairman title, leaving him as solely the chief executive. Voting on the proposal closes on Tuesday May 21 at the bank's annual meeting in Tampa, Florida.

Earlier this week Broadridge Financial Solutions Inc, which distributes proxy communications and collects votes, stopped giving early vote tallies to the investors who have proposed the measure. The Securities Industry and Financial Markets Association, a trade group whose members include JPMorgan, asked Broadridge to stop giving the sponsors that information, said Lyell Dampeer, a senior executive at the company.

Dimon and the board, who have been campaigning to defeat the measure, continue to get updates on incoming votes, and can adjust their campaign strategy accordingly. Investors calling for an independent chairman say that Broadridge's decision has put their campaign at a disadvantage.

Next week's vote has come to be seen as a referendum on Dimon and his ability to safely manage the biggest U.S. bank after its $6.2 billion "London Whale" loss derivatives trades last year.

Dampeer said Broadridge took the SIFMA letter as a directive from its customers which it had to obey. Corporations pay the firm to distribute proxy materials and collect votes.